Tuesday, 22 May 2012

Do I Need to Know How to Swim Before Learning to Scuba Dive?:

Once upon a time, when people wore bell-bottom pants and flowers in their hair, scuba diving had the reputation of being a physically demanding and dangerous activity best left to Navy Seals and Jacques Cousteau. Scuba diving has evolved since its early days and this is no longer the case. Advances in scuba equipment, the use of dive computers and sophisticated dive planning, as well as a better understanding of diving physiology have made diving safer and easier than it once was. Almost anyone can learn to dive.

Do I Need to Know How to Swim Before Learning to Scuba Dive?:

Not exactly. Before enrolling in a scuba course, prospective divers should be relatively comfortable in the water. While it is not necessary to have swum competitively in high school, a diving student should not be so terrified of the water that he is uncomfortable in the deep end of the swimming pool. To enroll in a one-day experience course, a person need only be comfortable in the water. To earn a scuba diving certification, a student diver must pass a watermanship assessment for scuba diving, which varies depending upon the organization and certification level. For example, one organization requires that students tread water/ float for 10 minutes, and swim 200 meters (or snorkel 300 meters) without stopping.

Am I Physically Fit for Scuba Diving?:

All scuba diving students must answer a scuba diving medical questionnaire before beginning a diving course. The high pressure a diver experiences underwater effects how his body functions in a variety of ways. Physical conditions that may not be bothersome, or even noticeable, in everyday life may be dangerous underwater. Lung problems (such as a collapsed lung or asthma), ear issues (such as problems with ear equalization), allergies, and certain diseases are all potentially dangerous underwater. Some medications are contraindicated for diving. Divers should carefully read, and then honestly answer the diving medical questionnaire before beginning to dive, and they should review it periodically throughout their diving careers.

Am I the Right Age for Scuba Diving?:

The age requirements for scuba diving vary amoung countries and scuba diving organizations. As a general rule, children aged 8 and above may scuba dive, depending upon their maturity level. Most diving organizations offer special children's courses in shallow, controlled conditions for kids aged 8 and above, and allow children 10 and older to enroll in certification courses. In the USA, most organizations require children to be 12 years old before certification. Learn more about children and scuba diving.
Currently, no upper age limit for scuba diving exists. In fact, my oldest open water certification student was a 82 year old female, and she turned out to be a great diver! Research into the risks associated with diving at an advanced age is ongoing.

Can I Scuba Dive With a Disability?:

Scuba diving is becoming an increasingly popular sport for people with physical disabilities. Special gear has been developed for divers who may have difficulty using standard dive gear, such as webbed gloves for divers who cannot swim with fins. However, in many cases specialized gear is not necessary. Divers are weightless and move freely underwater, so the weight of the scuba gear is not an impediment. Every new diver must relearn how to efficiently use his body in a completely foreign environment. Divers who have a physical disability are starting at exactly the same point as any other new diver – zero. Read about a hearing-impaired person learning to scuba dive.

Do I Have a Good Reason for Learning to Scuba Dive?:

The fact that most people can learn to scuba dive does not necessarily mean that everyone should. Before enrolling in a scuba diving course, a potential diver should consider his reasons for doing so. Divers who want to learn to dive because it seems like a risky adrenaline-filled sport should reconsider – properly done, recreational scuba diving is a sport about control and relaxation. Furthermore, a person should never take up scuba diving simply to please a spouse, parent or friend. While these people may serve as inspiration, for diving to be safe and enjoyable, a person needs to want to be underwater. The good news is that if you want to learn to dive, you most likely can. Welcome to the 70% of the world that most people never get to see!

All About Decompression Sickness

Also known as The Bends and Caisson Disease, Decompression Sickness is an illness that can affect divers or other people (such as miners) who are in a situation that involves pressure rapidly decreasing around the body.
DCS, as it is commonly know, is caused by a build up of nitrogen bubbles in the body. When we breathe, approximately 79 of the air we're breathing is nitrogen. As we descend in water, the pressure around our bodies increases, causing nitrogen to be absorbed into our body tissues. This is not actually harmful and it's quite possible for the body to continue to absorb nitrogen until it reaches a point called saturation, which is the point at which the pressure in the tissues equals the surrounding pressure.
The problem arises when this pressure needs to be released. In order to release the nitrogen slowly from the body, a diver must ascend slowly and carry out decompression stops if necessary - this allows the nitrogen to slowly seep out of the body tissues and either immediately revert to being a gas or to become tiny harmless bubbles which will eventually become revert to gas. This process is called "Off-gassing" and is normally carried out through the lungs.
If a diver ascends too fast and the nitrogen escapes the body tissue too quickly it becomes bubbles in the body and this leads to Decompression Sickness. The bubbles must normally be on the arterial side of the circulatory system to be harmful - they are usually harmless on the venous side. There are several types of Decompression Sickness:

Type I Decompression Sickness

Type I Decompression Sickness is the least serious form of Decompression Sickness. It normally involves only pain in the body and is not immediately life threatening. It is important to note that symptoms of Type I Decompression Sickness may be warning signs of more serious problems.
  • Cutaneous Decompression Sickness
    This is when the nitrogen bubbles come out of solution in skin capillaries. This normally results in a red rash, often on the shoulders and chest.
  • Joint and Limb Pain Decompression Sickness
    This type is characterized by aching in the joints. It is not known exactly what causes the pain as bubbles in the joint would not have this effect. The common theory is that it is caused by the bubbles aggravating bone marrow, tendons, and joints. The pain can be in one place or it can move around the joint. It is unusual for bisymmetrical symptoms to occur.

Type II Decompression Sickness

Type II Decompression Sickness is the most serious and can be immediately life-threatening. The main effect is on the nervous system.
  • Neurological Decompression Sickness
    When nitrogen bubbles affect the nervous system they can cause problems throughout the body. This type of Decompression Sickness normally shows as tingling, numbness, respiratory problems, and unconsciousness. Symptoms can spread quickly and if left untreated can lead to paralysis or even death.
  • Pulmonary Decompression Sickness
    This is a rare form of Decompression Sickness that occurs when bubbles form in lung capillaries. Fortunately, the majority of the time bubbles dissolve naturally through the lungs. However, it is possible for them to interrupt blood flow to the lungs which can lead to serious and life-threatening respiratory and heart problems.
  • Cerebral Decompression Sickness
    It is possible for bubbles that make their way into the arterial blood stream to move to the brain and to cause an arterial gas embolism. This is extremely dangerous and can be identified by symptoms such as blurred vision, headaches, confusion, and unconsciousness.

Other Forms of Decompression Sickness

Extreme tiredness is very common in cases of Decompression Sickness and can sometimes be the only symptom of Decompression Sickness present. It is not know what causes this but you should be aware that extreme fatigue could be a sign of more serious problems. It is also possible for Decompression Sickness to occur in the inner-ear. This is caused by bubbles forming in the cochlea's perilymph during decompression. The result can be hearing loss, dizziness, ringing of the ears, and vertigo.


Decompression Sickness can manifest itself in many different ways and has many different symptoms, but the most common symptoms are:
  • Extreme Fatigue
  • Joint and Limb Pain
  • Tingling
  • Numbness
  • Red Rash on Skin
  • Respiratory Problems
  • Heart Problems
  • Dizziness
  • Blurred Vision
  • Headaches
  • Confusion
  • Unconsciousness
  • Ringing of the Ears
  • Vertigo
  • Stomach Sickness 

Risk Factors

Every diver has a different level of risk of Decompression Sickness. Many risk factors are still not fully understood, but there are a few basic factors that doctors agree increase the chance of developing Decompression Sickness:
  • Bodyfat
    The theory is that nitrogen absorbs more easily into fat, so an overweight diver is at a greater risk of decompression sickness.
  • Exercise
    Interestingly, exercise has both a positive and negative effect. Exercise at least 12 hours before a dive seems to produce proteins that protect the body and decrease the risk of Decompression Sickness. On the other hand, exercise less than 12 hours before a dive can raise the number of gas micronuclei on which bubbles form and this increases the risk of Decompression Sickness. Exercise immediately after a dive increases the risk of bubbles forming as blood pressure is increased and bubbles can more easily be transferred from the venous to the arterial side of the circulatory system.
  • Gender
    Theoretically women should have a higher risk of Decompression Sickness due to the fact that women typically have a higher bodyfat content. However, this has not been proven in studies and it's possible that gender does not affect the chances of suffering from Decompression Sickness.
  • Age
    Generally, older people are at an increased risk of Decompression Sickness. This is due to less efficient circulatory and respiratory systems.
  • Fitness
    Fitness definitely decreases the risk of Decompression Sickness. A fitter body is able to tolerate more physical stress, including Decompression Sickness.
  • Dehydration
    Dehydration causes less blood to be available for gas exchange which makes it more difficult for the body to off-gas, increasing the risk of Decompression Sickness.
  • Injury and Illness
    Injury and illness can affect normal circulation, increasing the risk of Decompression Sickness.
  • Alcohol
    Consuming alcohol before or after a dive accelerates circulation which helps tissues to load with gas. Alcohol also dilates capillaries which can increase the rate of nitrogen released.
  • Carbon Dioxide
    Improper breathing can lead to elevated levels of carbon dioxide which interferes with the bodies ability to transport gas. This will lead to an increased chance of Decompression Sickness.
  • Cold
    It is generally believed by doctors that diving in cold water increases the risk of Decompression Sickness. This is due to the body working harder to keep warm as it becomes colder. Meaning that when the body is warmer it is able to absorb gas normally but as it becomes cold it has difficult offing the gas.
  • Altitude and Flying After Diving
    When ascending on land or in a plane, the atmospheric pressure changes and this increases the chances of Decompression Sickness. It is best not to ascend above 300 meters (1000 feet) or fly after diving. Consult the current flying after diving guidelines to know when it is safe to fly.
  • Patent Foramen Ovale (PFO) - Hole in the Heart
    As a fetus, a baby doesn't breathe and needs a way for blood to bypass the lungs until it is born. The body achieves this by having a small opening in the middle of the heart that allows blood to bypass the lungs. Normally, this hole would close within a year of birth, but in approximately 20-34 of people this does not happen, leaving a permanent opening in the heart. Usually, a flap grows over the opening and there is no effect. However, in some cases the flap allows blood to pass through the opening. This means that bubbles are more easily able to pass from the venous to the arterial side of the circulatory system, greatly increasing the risk of Decompression Sickness. It has been found that a large proportion of divers who suffered from Decompression Sickness had a PFO.
  • Reverse Profiles
    The jury is still out on reverse profiling, or making a deeper dive after a shallower dive. Theoretically it should increase the risk of Decompression Sickness, but this has not been proven scientifically. It would still be better to err on the side of caution.


    As there are many risk factors, there are also many methods of prevention. Here's a basic checklist that will help you lower your risk of suffering from Decompression Sickness:
    • Always ascend slowly and safely from every dive
    • Don't push your limits and do all required decompression stops
    • Keep physically fit and within a healthy weight range
    • Don't exercise within 12 hours of diving
    • Don't ascend to altitude or fly immediately after diving
    • Breathe normally throughout the dive, don't exert yourself or skip breathe
    • Make sure you're adequately hydrated before every dive
    • Don't drink alcohol before or after diving and never dive when hungover
    • Get checked out by a doctor to find out if you have a PFO
    • Avoid reverse profiling - just in case


    Immediate on the scene treatment consists of oxygen therapy and basic first aid. This should be followed as quickly as possible by recompression treatment in a recompression chamber. When treating Decompression Sickness the delay in beginning recompression treatment can be the biggest single cause of residual effects.


    PADI, Encyclopedia of Recreational Diving, 3rd Edition.
  • Saturday, 19 May 2012

    Dive computer buying tips

    Diving computers-watches measure the time and depth of dives to calculate a safe ascent in substitution of simple watches, depth gauges and diving tables or diving planners.

    Things to Consider When Buying a Scuba Diving Computer]

    1. Buttons- Are the buttons easy to use even with dive gloves on?

    2.Display Visibility- Can you read the display even in a low light situation. Are the numbers big enough? Does the background light up if needed? The key numbers you need to be able to see are Depth and Available Bottom Time Remaining. Everything else is a matter of preference.

    The more information you want to see, the smaller it will need to be to fit on the screen.

    3.Display Information- scuba diving computers can display a lot of information. Some things you may see are:
    • Current Depth
    • Max Depth
    • Bottom Time Remaining
    • Ascent Rate Monitors
    • Surface Interval Time
    • No Deco Time Limits For Next Dive
    • Water Temp
    And anything else under the sun you may want to know.

    You need to decide what information is important to you and buy a dive computer that displays that info.

    5. Power On and Off- Some diving computers begin to record the dive automatically and continue to run for hours after the last dive. Some need to be turned on. Are you the forgetful type or not?

    6. Air or Nitrox- Do you dive mixed gas now or plan to in the future? If so you need to buy a dive computer that lets you set the oxygen percentage. You can still use these computers to dive air just set the oxygen % to 21. If you don't plan on diving mixed gas you can save money and buy an air only scuba computer.

    5. Aggressive or conservative- An aggressive computer lets you stay down longer than a conservative one. Some diving computers will be aggressive shallow and conservative deep or vice versa. Some computers will let you adjust this.
    Research the scuba diving computer before hand and pick one that you are comfortable with.

    6. Altitude- Does it adjust automatically, manually or at all for diving at altitude.

    7.vAir-integrated or Stand alone- An air integrated computer will monitor tank pressure and calculate air and bottom time remaining. You can get models that either plug into a hose or even do this wirelessly.
    Stand alone computers don't record this info and you'll need to use a separate pressure gauge.

    8. Batteries- Can you change the batteries yourself or do you need to take it to the shop or even send it back to the manufacturer?

    9.Memory- How many dives will it record? Does it only record the last dive or does it record multiple (usually 10).
    If it only records the last dive you'll have to write the info down in between dives if you want to do a second.
    Does the memory wipe when you turn the power off? Will the dive computer retain that info if the batteries fail?

    10. Downloadable- Can you download the recorded dive to your laptop or desktop computer? Do you have to buy a separate software package or hardware (usb cord or other cable) to do so or does it come with everything?

    11. How do you "Wear" it?- Is it wrist mounted, console style or clip on?

    12. Warranty/Service- What type of warranty does it have? Can you get it serviced locally or will you have to send it to the manufacturer?
    There is obviously a lot to consider when looking at buying a scuba dive computer. Make a list of what you want/need and start reading reviews and manufacturers material until you find one that fits.

    The more options usually the more expensive it'll be.
    If you want a Nitrox compatible, wirelessly air integrated, expanded memory, satellite link up, gps, does everything for you except make the actual dive and it could probably do that remotely too, you're going to pay for it.

    The more bare bones it is the cheaper it'll be.